1// Allocators -*- C++ -*-
2
3// Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 2, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// You should have received a copy of the GNU General Public License along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19// USA.
20
21// As a special exception, you may use this file as part of a free software
22// library without restriction.  Specifically, if other files instantiate
23// templates or use macros or inline functions from this file, or you compile
24// this file and link it with other files to produce an executable, this
25// file does not by itself cause the resulting executable to be covered by
26// the GNU General Public License.  This exception does not however
27// invalidate any other reasons why the executable file might be covered by
28// the GNU General Public License.
29
30/*
31 * Copyright (c) 1996-1997
32 * Silicon Graphics Computer Systems, Inc.
33 *
34 * Permission to use, copy, modify, distribute and sell this software
35 * and its documentation for any purpose is hereby granted without fee,
36 * provided that the above copyright notice appear in all copies and
37 * that both that copyright notice and this permission notice appear
38 * in supporting documentation.  Silicon Graphics makes no
39 * representations about the suitability of this software for any
40 * purpose.  It is provided "as is" without express or implied warranty.
41 */
42
43/** @file ext/debug_allocator.h
44 *  This file is a GNU extension to the Standard C++ Library.
45 *  You should only include this header if you are using GCC 3 or later.
46 */
47
48#ifndef _DEBUG_ALLOCATOR_H
49#define _DEBUG_ALLOCATOR_H 1
50
51#include <stdexcept>
52
53_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
54
55  using std::size_t;
56
57  /**
58   *  @brief  A meta-allocator with debugging bits, as per [20.4].
59   *
60   *  This is precisely the allocator defined in the C++ Standard.
61   *    - all allocation calls operator new
62   *    - all deallocation calls operator delete
63   */
64  template<typename _Alloc>
65    class debug_allocator
66    {
67    public:
68      typedef typename _Alloc::size_type       	size_type;
69      typedef typename _Alloc::difference_type	difference_type;
70      typedef typename _Alloc::pointer       	pointer;
71      typedef typename _Alloc::const_pointer    const_pointer;
72      typedef typename _Alloc::reference       	reference;
73      typedef typename _Alloc::const_reference  const_reference;
74      typedef typename _Alloc::value_type       value_type;
75
76    private:
77      // _M_extra is the number of objects that correspond to the
78      // extra space where debug information is stored.
79      size_type 		_M_extra;
80
81      _Alloc			_M_allocator;
82
83    public:
84      debug_allocator()
85      {
86	const size_t __obj_size = sizeof(value_type);
87	_M_extra = (sizeof(size_type) + __obj_size - 1) / __obj_size;
88      }
89
90      pointer
91      allocate(size_type __n)
92      {
93        pointer __res = _M_allocator.allocate(__n + _M_extra);
94	size_type* __ps = reinterpret_cast<size_type*>(__res);
95	*__ps = __n;
96        return __res + _M_extra;
97      }
98
99      pointer
100      allocate(size_type __n, const void* __hint)
101      {
102        pointer __res = _M_allocator.allocate(__n + _M_extra, __hint);
103	size_type* __ps = reinterpret_cast<size_type*>(__res);
104	*__ps = __n;
105        return __res + _M_extra;
106      }
107
108      void
109      deallocate(pointer __p, size_type __n)
110      {
111	if (__p)
112	  {
113	    pointer __real_p = __p - _M_extra;
114	    if (*reinterpret_cast<size_type*>(__real_p) != __n)
115	      {
116		throw std::runtime_error("debug_allocator::deallocate"
117					 " wrong size");
118	      }
119	    _M_allocator.deallocate(__real_p, __n + _M_extra);
120	  }
121	else
122	  throw std::runtime_error("debug_allocator::deallocate null pointer");
123      }
124    };
125
126_GLIBCXX_END_NAMESPACE
127
128#endif
129